Pedantic Nitpicks:
Well, no, a ships size is also limited by:
1) the depth of shipping straits, channels and harbors it is intended to navigate
2) the width of those straits, channels and harbor basins
3) the depth and width -and- length of the locks of the any canals that are to be navigable by the vessel. *
4) the available tonnage of freight per round-trip on the intended trade route. (building a ship that sails half-empty most of the time is not a profit enhancing venture).
*: @ 2&3 e.g. Aframax, Chinamax, Malaccamax, Panamax, Q(atar)-max, Seawaymax, & Suezmax.
wastedfly wrote:[snip]
PPS. If we were building railroads today from scratch without the historical legacy of the cart industry and lack of power equipment able to move RR ballast easily, railroads would all be over 3 meters wide today. Probably over 5. If we had stronger steels able to be welded cheaply, all Ship bulk carriers would instantly triple or quadruple in size if not more. A ships size today is only limited by the materials available to us. They would be Mtons large if we could build them. An Mton of cargo is not that much when one starts looking at the gigantic tonnages being moved to centralized distribution centers.